Improvement in screw-propellers



J. BURSON.

SCREW-PROPELLER.

Nc.185,485. Patented Dec. 19, 1876.

Fly!

THE GRAPHIC CO N.Y.

UNITED STATES PATENT OFFICE.

JAMES BURSON, OF NEW YORK, N. Y.

IMPROVEMENT IN SCREW-PROPELLERS.

Specification forming part of Letters Patent N0. 185,485, dated December19, 1876; application filed August 31, 1876.

To all whom it may concern:

Be it known that I, JAMES BURSON, of the city, county, and State of NewYork, have invented a new and useful Improvement in Screw-Propellers;and I do hereby declare that the following is a full, clear, and exactwith each-other, and with openings through them, at their junction withthe hub, of a radius and area which not only provide for the readyclearance of any dead-water around the hub of the propeller, but whichprovide for an efl'ective action of the blades, one outside of theother, whereby the blades are prevented from materially interfering onewith the other, or from working in the currents or vortexes formed byeach other.

In the drawing, Figure 1 is a diagram in illustration of theconstruction of a twobladed propeller in accordance with my invention.Figs. 2 and 3 are elevations of the propeller in different directions,oblique to the axis thereof. Fig. 4 is a section in a plane parallelwith the axis on the line a; as; Fig. 5,

a section in a plane perpendicular to the axis.

on the line y 11 A is the hub of a submerged screw-propeller, having twoblades, B 0, arranged on opposite sides of the axis of the hub. Theseblades it is desirable to make of such comparative weights that theywill balance each other, but they are of unequal radius, and, to

give them the same propelling force, are of unequal area correspondingwith the difference of radius or leverage, and the amount of spacetraveled through by them respectively during each revolution of thepropeller. Both blades B and 0 should be constructed with openings b 0,through them at their junction with the hub. These openings not merelyprovide for a ready clearance of dead-water about or around the hub, orprevent the formation of dead-water at such part, but, so far as theone, b, of them in the blade B of larger radius is concerned, the sameprovides for said blade working during the rotation of the propelleroutside of or beyond the course described by the outer edge of thesmaller blade 0, whereby there is no material interference of one bladewith the action of the other, or liability of one blade to work in thecurrents or votexes formed by the different blades. To this end, theradius of the smaller blade G-.-that is, the distance from the center ofthe hub to the outer edge of said blade-should only approximate, andpreferably not exceed, but rather be less than, the distance from thecenter of the hub to the inner edge of the larger blade B.

In case of a third blade being used, it should bear the same relativeproportion to the opening 0 in the blade 0 that the blade 0 does to theopening 12 in the blade B, and so on for any number of differentialblades.

By reference to the drawing, Fig. l, in which the line d represents theaxis of the propeller, the line 0 the pitch-line of the blade B, ofgreater radius, and the linef the pitchline of the blade 0, of lesserradius, it will be seen that, While both blades are of the same pitch,they present different angles to the water, by reason of their differentlengths or radiuses, the smaller blade presenting the greatest angle.

There are other points which it will be well to observe in constructingthe propeller, as shown in the drawing, in order to give increasedefficiency. Thus, the arms g g of the blade B should be of a twistedconstruction, to prevent them dragging, and to give them a paddle-likeaction in or on the edges of the current produced by the blade 0. Theblade B also should be set inclining on the face, as at h, Fig. 5, tothrow the water toward the outer edge of said blade, where it is actedupon with the best effect, while the other blade 0 should be free fromany such inclination on its face.

I claim- A screw-propeller, constructed with two or more blades ofdifferent radiuses and different areas relatively with each other, andwith openings through them, substantially as and for the purposes hereinset forth.

JAMES BURSON.

Witnesses:

FRED. HAYNES, BENJAMIN W. HOFFMAN.

